I. Field
The present disclosure relates generally to communication, and more specifically to techniques for decoding data in a wireless communication system.
II. Background
In a wireless communication system, a transmitter typically processes (e.g., encodes and symbol maps) a packet of data to generate data symbols, which are modulation symbols for data. The transmitter further processes the data symbols to generate a modulated signal and transmits this signal via a wireless channel. The wireless channel distorts the transmitted signal with a channel response and further degrades the signal with noise and interference. A receiver receives the transmitted signal and processes the received signal to obtain data symbol estimates, which are estimates of the transmitted data symbols. The receiver then processes (e.g., demodulates and decodes) the data symbol estimates to obtain a decoded packet.
The system may employ hybrid automatic repeat request (H-ARQ) transmission to improve reliability for data transmission. With H-ARQ, the transmitter may send one or more transmissions for a packet, one transmission at a time. The receiver may receive each transmission sent by the transmitter and may attempt to decode different combinations of received transmissions to recover the packet. The receiver may send an acknowledgement (ACK) when the packet is decoded correctly, and the transmitter may send a transmission for a new packet upon receiving the ACK.
Packet decoding for H-ARQ transmission may be challenging for several reasons. First, the transmitter may send transmissions for packets in a discontinuous manner so that the receiver may not know with certainty whether or not a transmission for a packet has been received in a given frame. Second, the transmissions sent by the transmitter may not include information to indicate the first transmission (or start) of each packet. The receiver may then attempt to decode the received transmissions for various hypotheses, with each hypothesis corresponding to a different guess as to when a given packet was first sent. Decoding for many hypotheses may increase decoder complexity and/or require more buffering.
There is therefore a need in the art for techniques to efficiently decode data for H-ARQ.